The Department of Homeland Security is the third-largest federal department, and it operates through several distinct agencies rather than as a single unit. The main Homeland Security agencies are U.S. Customs and Border Protection, the U.S. Coast Guard, U.S. Citizenship and Immigration Services, U.S. Immigration and Customs Enforcement, the Transportation Security Administration, the Federal Emergency Management Agency, the U.S. Secret Service, and the Cybersecurity and Infrastructure Security Agency. Each was folded into DHS after the Homeland Security Act of 2002, each has its own statutory authority, and each handles a different piece of the department’s mission.
Border and Maritime Agencies
U.S. Customs and Border Protection is the agency you deal with at official ports of entry. Established under 6 U.S.C. § 211, CBP screens travelers and commercial cargo at airports, seaports, and land crossings for prohibited items and unauthorized entry.1Office of the Law Revision Counsel. 6 USC 211 – Establishment of U.S. Customs and Border Protection CBP officers have broader search authority at the border than domestic law enforcement does elsewhere. If your bag or phone has ever been inspected in an arrival hall, that was CBP.
The U.S. Border Patrol sits inside CBP as its law enforcement division, with responsibility for intercepting people trying to cross between official ports of entry. CBP officers work the crossings themselves; Border Patrol agents cover the ground in between.
The U.S. Coast Guard handles the maritime side and stands apart from the rest of DHS. It is a full military branch that also enforces civil law. Under 14 U.S.C. § 102, its duties divide into homeland security missions such as drug interdiction and port security, and non-homeland security missions such as search and rescue, marine safety, and environmental protection.2Office of the Law Revision Counsel. 14 USC 102 – Primary Duties Coast Guard personnel enforce federal law across the high seas and all U.S. waters. During hurricane season or a major spill, they are usually the first federal presence on the water.
Immigration: Two Agencies, Two Very Different Jobs
Immigration work inside DHS splits between two agencies. Mixing them up causes real problems, so the difference matters.
U.S. Citizenship and Immigration Services
USCIS processes immigration benefits: green card petitions, asylum applications, work permits, and naturalization. Established under 6 U.S.C. § 271, it adjudicates applications and decides who qualifies for legal status.3Office of the Law Revision Counsel. 6 USC 271 – Establishment of Bureau of Citizenship and Immigration Services The agency is almost entirely fee-funded, meaning applicants cover the cost of their own processing.
Filing fees are not small. The naturalization application (Form N-400) currently costs $760 on paper or $710 online, with a reduced rate of $380 for applicants who qualify based on income.4USCIS. N-400, Application for Naturalization Attorney costs are separate. Processing times vary widely by application type and by field office.
U.S. Immigration and Customs Enforcement
ICE handles enforcement. Organized under 6 U.S.C. § 252, it investigates cross-border criminal activity including human trafficking, drug smuggling, and financial crimes.5Office of the Law Revision Counsel. 6 USC 252 – U.S. Immigration and Customs Enforcement Its Enforcement and Removal Operations division identifies, detains, and removes people who have violated immigration law or been ordered deported by an immigration judge. Homeland Security Investigations, ICE’s other major division, pursues transnational crime well beyond immigration, including intellectual property theft and money laundering.
Transportation Security Administration
The Transportation Security Administration is the DHS agency most Americans encounter. Created under 49 U.S.C. § 114, TSA is responsible for security across all transportation modes, though aviation absorbs most of its workforce.6Office of the Law Revision Counsel. 49 USC 114 – Transportation Security Administration Transportation Security Officers staff checkpoints at every commercial airport. Federal Air Marshals also work for TSA, flying armed and undercover on commercial flights. TSA regulates surface transportation security too, including mass transit and freight rail, though those programs are much less visible than airport screening.
Bringing a prohibited item to a checkpoint has real financial consequences. The statutory maximum civil penalty for an individual aviation security violation is $100,000 under the FAA Reauthorization Act of 2024.7Office of the Law Revision Counsel. 49 USC 46301 – Civil Penalties TSA’s fine schedule for firearms at checkpoints runs from $3,000 to over $17,000 depending on whether the weapon is loaded and the circumstances. Even a genuine mistake with a firearm in a carry-on will cost thousands and delay your travel.
REAL ID at the Checkpoint
As of May 7, 2025, TSA requires a REAL ID-compliant driver’s license, state identification card, or another acceptable form of ID for domestic flights.8Transportation Security Administration. TSA Publishes Final Rule on REAL ID Enforcement Beginning May 7, 2025 A standard pre-REAL ID license no longer works. If your license doesn’t carry a star or similar marking in the upper corner, check with your state’s motor vehicle agency before you fly. A valid U.S. passport also satisfies the requirement.
Federal Emergency Management Agency
FEMA leads the federal government’s response when a disaster overwhelms state and local resources. Under 6 U.S.C. § 313, its mission is to reduce loss of life and property from natural disasters, terrorism, and other catastrophic events through preparedness, response, recovery, and mitigation.9Office of the Law Revision Counsel. 6 USC 313 – Federal Emergency Management Agency
Federal disaster aid doesn’t flow automatically. Under the Stafford Act, a governor must request a presidential disaster declaration, certifying that the situation exceeds the state’s ability to respond and committing state resources to cost-sharing.10Office of the Law Revision Counsel. 42 USC 5170 – Procedure for Declaration Tribal leaders can request declarations independently. Only after the President approves does FEMA begin distributing federal funds for temporary housing, home repairs, debris removal, and infrastructure reconstruction. This is where most people misread the process. FEMA does not show up on its own. Someone has to ask, and the request has to clear a legal threshold.
FEMA also runs the National Flood Insurance Program, which matters because standard homeowners policies do not cover flood damage. Separate public assistance programs help local governments restore damaged roads, utilities, and public buildings after a declared disaster.
U.S. Secret Service
The Secret Service is known for protecting the President, but its original job was investigating financial crime, and that work continues. Under 18 U.S.C. § 3056, the agency carries a dual mandate: physical protection of designated officials and foreign dignitaries, and criminal investigation of fraud targeting the U.S. financial system.11Office of the Law Revision Counsel. 18 U.S. Code 3056 – Powers, Authorities, and Duties of United States Secret Service Its investigative work covers counterfeiting, electronic fund transfer fraud, identity theft, and access device fraud.
Counterfeiting U.S. currency carries a federal prison sentence of up to 20 years.12Office of the Law Revision Counsel. 18 USC 471 – Obligations or Securities of United States The agency’s investigative focus has increasingly shifted toward cybercrime and cryptocurrency fraud alongside its traditional counterfeiting work.
Cybersecurity and Infrastructure Security Agency
CISA is the newest major DHS component, established under 6 U.S.C. § 652. It serves as the federal government’s lead advisor on protecting critical infrastructure, from power grids and water systems to communication networks and financial institutions.13Office of the Law Revision Counsel. 6 USC 652 – Cybersecurity and Infrastructure Security Agency The agency gives technical assistance to government offices and private companies, helping them find vulnerabilities before attackers do. Under 6 U.S.C. § 655, CISA also delivers threat analysis and warnings to state and local governments and private operators of critical systems.14Office of the Law Revision Counsel. 6 U.S. Code 655 – Enhancement of Federal and Non-Federal Cybersecurity
CISA operates around the clock, monitoring threats and issuing alerts. Government advisories about software vulnerabilities or major breaches typically come through CISA. Its role has grown as cyberattacks on hospitals, pipelines, and local governments have become more frequent.
Cyber Incident Reporting
The Cyber Incident Reporting for Critical Infrastructure Act (CIRCIA) requires covered entities to report significant cyber incidents to CISA within 72 hours of reasonably believing one has occurred. Ransomware payments must be reported within 24 hours.15CISA. Cyber Incident Reporting for Critical Infrastructure Act of 2022 (CIRCIA) The clock starts on reasonable belief, not on confirmation. CISA is still finishing the rulemaking, so the mandatory reporting requirements are not yet in force, but organizations in critical infrastructure sectors should be preparing.
Filing a Complaint About a DHS Agency
Every DHS agency answers to the department’s Office of Inspector General, which investigates allegations of waste, fraud, abuse, and misconduct. If you have a complaint about how a DHS agency handled your case, or if you witnessed something wrong, you can file a report through the OIG’s online hotline. The form lets you remain anonymous, request confidentiality, or fully identify yourself, and you certify your statements are truthful under penalty of federal law.16DHS Office of Inspector General. OIG Hotline Complaint Form This channel is separate from any internal complaint process within the agency itself, and the OIG can investigate independently.